1. Technical Field
Example embodiments relate to a data storage device, e.g., a data storage device having magnetic domain wall motion, which may write, store, and erase data by inducing magnetic domain wall motion.
2. Description of the Related Art
Recent developments in the information industry may have led to increased research relating to improved techniques for processing larger quantities of data as well as improved data storage devices for storing the larger quantities of data. A data storage device (e.g., hard disc drive (HDD)) may include a read/write head and a rotating recording medium and may have a capacity that may be up to about 100 gigabytes (GB) or more. However, a data storage device (e.g., HDD) having a rotating portion may be susceptible to abrasion, and failures may be more likely to occur during the drive of the data storage device, thereby decreasing reliability.
In recent years, increased research regarding data storage devices using magnetic domain wall motion has been conducted. A magnetic minute region constituting a magnetic body may be referred to as a magnetic domain. The directions of magnetic moment as a result of electron spins may be essentially the same in the magnetic domain. The size and magnetic polarization of the magnetic domain may be appropriately controlled using the shape and size of a magnetic material and external energy. A magnetic domain wall may refer to a boundary region between magnetic domains having different magnetic polarizations. The magnetic domain wall may be moved in response to a magnetic field or current applied to a magnetic material.
FIGS. 1A through 1C are diagrams illustrating the conventional principle of magnetic domain wall motion. Referring to FIG. 1A, a magnetic layer having a first magnetic domain 11, a second magnetic domain 12, and a magnetic domain wall 13 corresponding to a boundary region between the first and second magnetic domains 11 and 12, respectively, may be prepared.
Referring to FIG. 1B, when a magnetic field is externally applied in a direction from the second magnetic domain 12 to the first magnetic domain 11, the magnetic domain wall 13 may move in the direction from the second magnetic domain 12 to the first magnetic domain 11. Thus, the magnetic domain wall 13 may move in essentially the same direction as the direction in which the external magnetic field is applied. Similarly, when a magnetic field is applied in a direction from the first magnetic domain 11 to the second magnetic domain 12, the magnetic domain wall 13 may move in the direction from the first magnetic domain 11 to the second magnetic domain 12.
Referring to FIG. 1C, when a current (not shown) is externally supplied in a direction from the first magnetic domain 11 to the second magnetic domain 12, the magnetic domain wall 13 may move in a direction from the second magnetic domain 12 to the first magnetic domain 11. When the current is supplied, electrons may flow in an opposite direction to the direction in which the current is supplied, and the magnetic domain wall 13 may move in essentially the same direction as the direction in which the electrons flow. Thus, the magnetic domain wall 13 may move in an opposite direction to the direction in which the external current is supplied. Similarly, when current is supplied in the direction from the second magnetic domain 12 to the first magnetic domain 11, the magnetic domain wall 13 may move in the direction from the first magnetic domain 11 to the second magnetic domain 12.
The principle of magnetic domain wall motion may be applied to data storage devices, e.g., HDDs or nonvolatile random access memories (RAMs). For example, a nonvolatile memory device that writes and reads data ‘0’ or data ‘1’ may be embodied on the principle that a voltage of a magnetic material having magnetic domains, which may be magnetized in specific directions, and a magnetic domain wall corresponding to a boundary region between the magnetic domains may be changed as a result of the motion of the magnetic domain wall. The position of the magnetic domain wall may be changed by supplying a predetermined current to a linearly-shaped magnetic material so that the nonvolatile memory device may write and read data. Therefore, a higher integrated device having a simpler structure may be achieved.
When the principle of the magnetic domain wall motion is applied to data storage devices (e.g., HDDs or nonvolatile RAMs), multiple magnetic layers and a connection layer disposed between the magnetic layers may be provided to increase data storage density. Data may be written or read by moving a magnetic domain wall between the magnetic layers. However, when current is supplied through the connection layer interposed between the magnetic layers to move the magnetic domain wall, current density may be reduced because of leakage, thereby hindering the motion of the magnetic domain wall.